Sound transmitter



May 29, 1923.

1,456,742 P. V. ROONEY SOUND TRANSMITTER Fiieq April 4, 1921 Patented ay 29, 192.3.

PAUL V. ROONEY, OF MORRISTDWN, NEW JERSEY.

SOUND TRANSMITTER.

Application filed April 4,

To all whom it may concern:

Be it knownthat I, PAUL V. RooNEY, a citizen of the United States, residing at Morristown, in the county of Morris and State of New Jersey, have invented certain new and useful Improvements in Sound Transmitters, of which the following is a specification.

This invention relates to electrical sound transmitting devices, and while 1t has particular reference, and will be so described herein, to telephone transmitters, I wish it to be distinctly understood that it is susceptible in many of itsaspects of a much broader application.

Among the objects of the invention is to provide an efficient mechanism for controlling the large powers met with in the operation of wireless or radio-telephony. In the usual telephone transmitter the resistance member consists of a mass of loose carbon granules adjacent to the vibrating diaphragm, but in currents of high power there is a tendency for such loose particles to fuse and cake thereby reducing if not impairing the eficiency of the instrument. Whereas the transmission of articulate words or the like is dependent upon a ready variation in the resistance device or member, I have provided a resistance device comprising one or more one piece resistance members,each having the facility of relatively free variation in position and resistance function, while at the same time it is of an integral construction and so is adapted for the carrying of maximum currents without deterioration or failure.

Another object of the invention is to provide a resistance device comprising two resistance members, each of which is integral in its nature throughout its length, and both of which are of relatively great length and eiribility and vet which coincide with each other potentially from one end to the other subject to such variations in contact between them as are necessary for the proper operation of the instrument.

Another object of the invention is to provide a sound transmitting instrument including a resistance device including a one piece vibratory resistance member` co-operating throughout its length with a similarly shaped resistance member, the latter of which is relatively fixed as to vibration but is readily and delicately adjustable so as to vary 1921. Serial No. 458,513.

the effective variability of length of the combined or co-operating resistance members.

A further object of the invention is to p rovide a resistance device comprising a vibratory resistance member 'having a perfectly smooth and relatively flat surface arranged to co-operate potentially with another member having a smooth flat surface.

.With the foregoing and other objects in view the 1nvention consists in the arrangef ment and combination 0f parts hereinafter described and claimed, and while the invention is not restricted to the exact details of construction disclosed or suggested herein, s till for the purpose of illustrating a practical embodiment thereof reference is had 'to the accompanying drawings, in which like reference characters designate the same. parts in the several views, and in which- Figure 1 is a vertical sectional view of a high powered telephone transmitter indicating somewhat diagrammatically the application of my improvement.

Fig. 2 is an enlarged sectional detail of the resistance device.

Fig. 3 is a plan view of one of the resistance members showing a preferred form of the same. A

Referring now more specifically to the drawings I indicate a transmitter in which the mouth piece 10 is attached to a cap 11 constituting a closure for the airtight resistance chamber 12 of a casing 13 provided with a relatively large cavity 14 for the circulation of a cooling medium such as water through which the heat generated as a result of the flow of a heavy current may be dissipated.

The diaphragm 15 is secured within` the chamber 12 in position to be vibrated by the voice or other sound passing inward through the mouth piece, the diaphragm being secured at its periphery in a ring of insulation 16 in any well known manner. One conductor 17 of the electric current is attached as at 18 to the diaphragm or to some member associated directly with the diaphragm. The other conductor 19 also leads through the casing wall, both conductors being preferably sealed airtight in a plate 24 of insulation, connected as by screws 25 to the wall 26 between the chambers 12 and 14.

As above 'premised the efficiency and reliability of a resistance device for a high readily variable effective length must yet be one which is either integral or substantially of one piece or unbroken c'ontinulty throughout its length and at all times. To this end, therefore, I provide a resistance device comprising preferably two resistance members 21 and 22, both made similar to each other with respect to surface registryand secured firmlyor substantially integrally together at their peripheries as by means of screws 23 secured in said plate 24.

As shown herein as a practical embodiment of my invention, but without being unnecessarily limited to such design, each member 21 or 22 is essentially a disk, the

face of a member 21 or 22 lying against or adjacent to the other member is formed substantially flat and perfectly smooth and with a high polish so that when the spirals are assembled one directly above the other or in contact from one end to the other of the resistance rods 30 their surfaces will be brought into perfect contact throughout whatever portion of their len th may be made eli'ective at any time. hese resistance disks may be made of carbon or any other suitable material. The member 22, being relatively stationary in practice, may have a form or design, in directions parallel to the vibration of the member 21, diilering from the form of the member 21, as indicated in Fig. 2l.

The diaphragm 15 is connected electrically, as by means of a screw or post 31, to the center 28 of the member 21, the head of the screw being countersunk at 32 in the resistance member so as to prevent any possible direct contact with the other resistance member or connecting means. The screw 31 is shown locked in place with respect to the disk center 28 as by means of a nut 33, and the connection between the screw and the diaphragm is made adjustable by means of nuts 34- applied on opposite sides ofA the diaphragm and adjacent to a cushion 35. The effective length of the screw or connection 31 is so determined as to cause the center 28 of the member 21 to be spaced slightly from the central portion of the other member when in normal position, and the cross section and length of rod of the vibratory resistance member are so chosen that the natural period of vibration thereof when connected with the diaphragm is below that usually met with in speech, otherwise considcrable difficulty would be encountered by a disproportionate flow of energy when the resonant frequency of the combination is reached. It will be borne in mind, however, that irrespective of the clearance or space between the centers 28 of the two resistance members, either normally or in practice, their peripheries at least are maintained clamped together or otherwise suhstantially integral, so 'that the course of the flow of energy must be from the diaphragm and screw through the center 28 and rod 30 of the vibratory member outward along the spiral until the outer end of the spiral makes contact with the corresponding portion of the relatively stationary member 22. Thence the force of the current is inward along the member 22 to its center 28, whence it passes to the conductor 19, as will be understood. Said conductor 19 is indicated as attached to a screw 36 serving to secure a block 37 of insulation to the under surface of the center 28. The adjustment of the screw 31 as to effective length may not be more than an approximation, and hence is one ordinarily ei'ected at the factory when the parts are assembled. To effect a more delicate and hence satisfactory adjustment as to clearance between the two centers 28 so as 'to realize the highest degree of efiiciency of the two co-operating spiral rods, means is provided to adjust the center 28 of the relatively stationary disk 22, by means preferably available at any time after assemblage of the instrument. To 'this end I show as a practical means a screw 38 tapped through a plug or base 39 secured in the wall 26, the screw being accessible by means of an instrument inserted through a hole 40 in the bottom of the casing 13. This screw 38 bears against the block 37 and so the eective position of the center 28 of the member 22 may be readily determined and established at any time and without disturbing the adjustment or connection between the diaphragm and the vibratory member 21.

From the specific description of mechanism set forth above the operation may be readily appreciated as follows: With the sound to be transmitted making impact against the outer surface of the diaphragm, the diaphragm and the Vresistance member attached there to will vibrate according to the character and force of the sound. Assuming that after adjustment of the instrument the normal point of contact between the two resistance members is somewhere along the two rods, as at the point it folscrew connected thereto is varied. Moreover, because of the smooth and true surface of contact between the two resistance rods there results such a gradual uniformity of variation in effective length of resistance rods as to make the instrument unusuall effective in service, and because of this uniformity of variation in contact point the effective adjustments at the screws 31 and 36, especially the latter, may be very delicate and yet at the same time thoroughly reliable.

The necessity for regulation and fiexibili'ty will be understood from the fact that a conductor having resistance and carrying a current of appreciable value, large quantities of heat are generated, and this heat expands the conductors in all directions, and in the case of the opposed spirals might throw the convolutions more or less out of registry or contact, it being remembered that the amplitude of vibration of the member 21 does not ordinarily exceed a few thousandths of an inch, which while sufficient for the accomplishment of the purpose must be quite closely adhered to, and this may be readily accomplished by reason of the adjustment at the screw 38.

Since the diaphragm 15 is imperforate and the chamber 12 between it and the casing wall 26 is preferably substantially airtight, the conductors 17 and 19 being sealed in the supporting ring of insulation, I provide as a suitable means to insure freedom of action of the diaphragm, one or more air ports 20, shown as being formed through the plug 39 through which the adjustment screw 38 is pro'ected. It will be noted also that the head o this screw co-operating with the end of the plug serves as a stop shoulder to limit the upward displacement of the center of the resistance member 22, so that no breakage nor damage thereto can result.

The relatively stationary resistance member 22 is preferably so constructed that the cross sectional area of the rod portion thereof is variable between the center and Inarginal portions thereof. This fact is illustrated in Figs. 1 and 2 in the formation of the concavity in the lower side thereof. In other words, extending inward toward the center from the peripheral or outer end portion of the rod at the points where variable contact is made in practice between it and the rod portion of the upper resistance member 21, the cross section of the rod of the stationary member decreases inward at least to about the radial middle portion thereof. By this fact or its equivalent I am better able to approximate uniformity of results and to reduce the voice distortion 'to a minimum. Consistent with the well known principle that resistance varies directly as to length and inversely as to cross section it follows that while the rod becomes shorter between the points of contact at w and the center the cross section of the lower rod becomes correspondingly smaller.

I claim:

1. In a variable resistance device, two approximately fiat members comprising a like number of fiat spirals arranged directly one above the other, the cross section of each spiral being so shaped that the adacent surfaces of the mating spirals are a apted to have direct fiat contact one with the other, means anchoring the marginal portions of the members firmly together, while the central ortions thereof at the center of the spira s are both movable toward and from each other, and conductor means connected to said respective central portions of the spirals.

2. ln a variable resistance device, the coinbination of a pluralityof resistance members having fixed direct contact with each other at certa-in portions and being normally spaced from each other at portions remote from the portions in direct contact, and means to adjust each of said members towardand from the other, one of said members being adapted to vibrate, and the effective length of the spaced portion of the members in practice being variable as a result of said vibration.

3. in a variable resistance device, the combination of a plurality of resistance members, each in the form of a spiral rod, said members having fixed direct physical contact with each other at certain portions and being normally spaced from each other at other portions, the convoluted portions of Saidmembers being spaced from all supporting means and so are substantially self supporting by virtue of their own tensile strength, one of said members being adapted to vibrate, and the effective length of the spaced portions of the members in practice being variable as a result of said vibration.

4. In a variable resistance apparatus, the combination of a diaphragm, a conductor leading to the diaphragm, a conductor remote from the diaphragm, a resistance device between the diaphragm and the latter conductor, and means to variably connect the diaphragm with said resistance device, said resistance device comprising a substantially flat member formed with a spiral slot whereby the resistance member is in the nature of a long rod, the conductor connections being effectively at opposite portions of the rod.

5. A device as set forth in claim 4 in which the resistance device consists of two similarly constructed spirals superposed one directly upon the other and having constant contact at certain portions and being normally spaced from each other at other portions.

6. ln a sound transmitter the combination with a diaphragm, a conductor associated with the diaphragm, and a conductor remote from the diaphragm, of a. variable resistance device between the two conductors and remote from the diaphragm, said resistance device consisting of a substantially fiat spiral memberinherently vibratory and approximately parallel to the diaphragm and a relatively stationary member so co-operating with the spiral member as 'to va the effective length thereof coincident with its vibration, and means to variably connect the spiral resistance member to the diaphragm.

7. A device as set forth in claim 2 in which the cross section of at least one of the resistance members is variable to comreadme pensate for the variation in resistance due to effective changes in length thereof in practice.

8. A device as set forth in claim 2in which one of the resistance members is a spiral rod of variable cross section between its ends While the other resistance memberV which is vibratory in (bo-operating with the spiral rod produces a varlation in effective length ofthe rod, whose resistance tending to diminish as its length diminishes is more or less increased due to the reduction in its cross section.

In testimony whereof I aix my si ature PAUL V. ROO EY. 

